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[PATCH] improve precision of process accounting.
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The unit of the cputime accouting values that are stored per process is
currently a microsecond. The CPU timer has a maximum granularity of
2**-12 microseconds. There is no benefit in storing the per process values
in the lesser precision and there is the disadvantage that the backend
has to do the rounding to microseconds. The better solution is to use
the maximum granularity of the CPU timer as cputime unit.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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Martin Schwidefsky committed Dec 31, 2008
1 parent 79741dd commit aa5e97c
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Showing 5 changed files with 85 additions and 96 deletions.
42 changes: 21 additions & 21 deletions arch/s390/include/asm/cputime.h
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Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,7 @@

#include <asm/div64.h>

/* We want to use micro-second resolution. */
/* We want to use full resolution of the CPU timer: 2**-12 micro-seconds. */

typedef unsigned long long cputime_t;
typedef unsigned long long cputime64_t;
Expand Down Expand Up @@ -53,9 +53,9 @@ __div(unsigned long long n, unsigned int base)
#define cputime_ge(__a, __b) ((__a) >= (__b))
#define cputime_lt(__a, __b) ((__a) < (__b))
#define cputime_le(__a, __b) ((__a) <= (__b))
#define cputime_to_jiffies(__ct) (__div((__ct), 1000000 / HZ))
#define cputime_to_jiffies(__ct) (__div((__ct), 4096000000ULL / HZ))
#define cputime_to_scaled(__ct) (__ct)
#define jiffies_to_cputime(__hz) ((cputime_t)(__hz) * (1000000 / HZ))
#define jiffies_to_cputime(__hz) ((cputime_t)(__hz) * (4096000000ULL / HZ))

#define cputime64_zero (0ULL)
#define cputime64_add(__a, __b) ((__a) + (__b))
Expand All @@ -64,7 +64,7 @@ __div(unsigned long long n, unsigned int base)
static inline u64
cputime64_to_jiffies64(cputime64_t cputime)
{
do_div(cputime, 1000000 / HZ);
do_div(cputime, 4096000000ULL / HZ);
return cputime;
}

Expand All @@ -74,13 +74,13 @@ cputime64_to_jiffies64(cputime64_t cputime)
static inline unsigned int
cputime_to_msecs(const cputime_t cputime)
{
return __div(cputime, 1000);
return __div(cputime, 4096000);
}

static inline cputime_t
msecs_to_cputime(const unsigned int m)
{
return (cputime_t) m * 1000;
return (cputime_t) m * 4096000;
}

/*
Expand All @@ -89,13 +89,13 @@ msecs_to_cputime(const unsigned int m)
static inline unsigned int
cputime_to_secs(const cputime_t cputime)
{
return __div(cputime, 1000000);
return __div(cputime, 2048000000) >> 1;
}

static inline cputime_t
secs_to_cputime(const unsigned int s)
{
return (cputime_t) s * 1000000;
return (cputime_t) s * 4096000000ULL;
}

/*
Expand All @@ -104,7 +104,7 @@ secs_to_cputime(const unsigned int s)
static inline cputime_t
timespec_to_cputime(const struct timespec *value)
{
return value->tv_nsec / 1000 + (u64) value->tv_sec * 1000000;
return value->tv_nsec * 4096 / 1000 + (u64) value->tv_sec * 4096000000ULL;
}

static inline void
Expand All @@ -114,12 +114,12 @@ cputime_to_timespec(const cputime_t cputime, struct timespec *value)
register_pair rp;

rp.pair = cputime >> 1;
asm ("dr %0,%1" : "+d" (rp) : "d" (1000000 >> 1));
value->tv_nsec = rp.subreg.even * 1000;
asm ("dr %0,%1" : "+d" (rp) : "d" (2048000000UL));
value->tv_nsec = rp.subreg.even * 1000 / 4096;
value->tv_sec = rp.subreg.odd;
#else
value->tv_nsec = (cputime % 1000000) * 1000;
value->tv_sec = cputime / 1000000;
value->tv_nsec = (cputime % 4096000000ULL) * 1000 / 4096;
value->tv_sec = cputime / 4096000000ULL;
#endif
}

Expand All @@ -131,7 +131,7 @@ cputime_to_timespec(const cputime_t cputime, struct timespec *value)
static inline cputime_t
timeval_to_cputime(const struct timeval *value)
{
return value->tv_usec + (u64) value->tv_sec * 1000000;
return value->tv_usec * 4096 + (u64) value->tv_sec * 4096000000ULL;
}

static inline void
Expand All @@ -141,12 +141,12 @@ cputime_to_timeval(const cputime_t cputime, struct timeval *value)
register_pair rp;

rp.pair = cputime >> 1;
asm ("dr %0,%1" : "+d" (rp) : "d" (1000000 >> 1));
value->tv_usec = rp.subreg.even;
asm ("dr %0,%1" : "+d" (rp) : "d" (2048000000UL));
value->tv_usec = rp.subreg.even / 4096;
value->tv_sec = rp.subreg.odd;
#else
value->tv_usec = cputime % 1000000;
value->tv_sec = cputime / 1000000;
value->tv_usec = cputime % 4096000000ULL;
value->tv_sec = cputime / 4096000000ULL;
#endif
}

Expand All @@ -156,13 +156,13 @@ cputime_to_timeval(const cputime_t cputime, struct timeval *value)
static inline clock_t
cputime_to_clock_t(cputime_t cputime)
{
return __div(cputime, 1000000 / USER_HZ);
return __div(cputime, 4096000000ULL / USER_HZ);
}

static inline cputime_t
clock_t_to_cputime(unsigned long x)
{
return (cputime_t) x * (1000000 / USER_HZ);
return (cputime_t) x * (4096000000ULL / USER_HZ);
}

/*
Expand All @@ -171,7 +171,7 @@ clock_t_to_cputime(unsigned long x)
static inline clock_t
cputime64_to_clock_t(cputime64_t cputime)
{
return __div(cputime, 1000000 / USER_HZ);
return __div(cputime, 4096000000ULL / USER_HZ);
}

#endif /* _S390_CPUTIME_H */
40 changes: 20 additions & 20 deletions arch/s390/include/asm/lowcore.h
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Original file line number Diff line number Diff line change
Expand Up @@ -67,11 +67,11 @@
#define __LC_SYNC_ENTER_TIMER 0x248
#define __LC_ASYNC_ENTER_TIMER 0x250
#define __LC_EXIT_TIMER 0x258
#define __LC_LAST_UPDATE_TIMER 0x260
#define __LC_USER_TIMER 0x268
#define __LC_SYSTEM_TIMER 0x270
#define __LC_LAST_UPDATE_CLOCK 0x278
#define __LC_STEAL_CLOCK 0x280
#define __LC_USER_TIMER 0x260
#define __LC_SYSTEM_TIMER 0x268
#define __LC_STEAL_TIMER 0x270
#define __LC_LAST_UPDATE_TIMER 0x278
#define __LC_LAST_UPDATE_CLOCK 0x280
#define __LC_RETURN_MCCK_PSW 0x288
#define __LC_KERNEL_STACK 0xC40
#define __LC_THREAD_INFO 0xC44
Expand All @@ -89,11 +89,11 @@
#define __LC_SYNC_ENTER_TIMER 0x250
#define __LC_ASYNC_ENTER_TIMER 0x258
#define __LC_EXIT_TIMER 0x260
#define __LC_LAST_UPDATE_TIMER 0x268
#define __LC_USER_TIMER 0x270
#define __LC_SYSTEM_TIMER 0x278
#define __LC_LAST_UPDATE_CLOCK 0x280
#define __LC_STEAL_CLOCK 0x288
#define __LC_USER_TIMER 0x268
#define __LC_SYSTEM_TIMER 0x270
#define __LC_STEAL_TIMER 0x278
#define __LC_LAST_UPDATE_TIMER 0x280
#define __LC_LAST_UPDATE_CLOCK 0x288
#define __LC_RETURN_MCCK_PSW 0x290
#define __LC_KERNEL_STACK 0xD40
#define __LC_THREAD_INFO 0xD48
Expand Down Expand Up @@ -252,11 +252,11 @@ struct _lowcore
__u64 sync_enter_timer; /* 0x248 */
__u64 async_enter_timer; /* 0x250 */
__u64 exit_timer; /* 0x258 */
__u64 last_update_timer; /* 0x260 */
__u64 user_timer; /* 0x268 */
__u64 system_timer; /* 0x270 */
__u64 last_update_clock; /* 0x278 */
__u64 steal_clock; /* 0x280 */
__u64 user_timer; /* 0x260 */
__u64 system_timer; /* 0x268 */
__u64 steal_timer; /* 0x270 */
__u64 last_update_timer; /* 0x278 */
__u64 last_update_clock; /* 0x280 */
psw_t return_mcck_psw; /* 0x288 */
__u8 pad8[0xc00-0x290]; /* 0x290 */

Expand Down Expand Up @@ -343,11 +343,11 @@ struct _lowcore
__u64 sync_enter_timer; /* 0x250 */
__u64 async_enter_timer; /* 0x258 */
__u64 exit_timer; /* 0x260 */
__u64 last_update_timer; /* 0x268 */
__u64 user_timer; /* 0x270 */
__u64 system_timer; /* 0x278 */
__u64 last_update_clock; /* 0x280 */
__u64 steal_clock; /* 0x288 */
__u64 user_timer; /* 0x268 */
__u64 system_timer; /* 0x270 */
__u64 steal_timer; /* 0x278 */
__u64 last_update_timer; /* 0x280 */
__u64 last_update_clock; /* 0x288 */
psw_t return_mcck_psw; /* 0x290 */
__u8 pad8[0xc00-0x2a0]; /* 0x2a0 */
/* System info area */
Expand Down
4 changes: 2 additions & 2 deletions arch/s390/include/asm/system.h
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Original file line number Diff line number Diff line change
Expand Up @@ -99,7 +99,7 @@ static inline void restore_access_regs(unsigned int *acrs)
prev = __switch_to(prev,next); \
} while (0)

extern void account_vtime(struct task_struct *);
extern void account_vtime(struct task_struct *, struct task_struct *);
extern void account_tick_vtime(struct task_struct *);
extern void account_system_vtime(struct task_struct *);

Expand All @@ -121,7 +121,7 @@ static inline void cmma_init(void) { }

#define finish_arch_switch(prev) do { \
set_fs(current->thread.mm_segment); \
account_vtime(prev); \
account_vtime(prev, current); \
} while (0)

#define nop() asm volatile("nop")
Expand Down
2 changes: 2 additions & 0 deletions arch/s390/include/asm/thread_info.h
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Original file line number Diff line number Diff line change
Expand Up @@ -47,6 +47,8 @@ struct thread_info {
unsigned int cpu; /* current CPU */
int preempt_count; /* 0 => preemptable, <0 => BUG */
struct restart_block restart_block;
__u64 user_timer;
__u64 system_timer;
};

/*
Expand Down
93 changes: 40 additions & 53 deletions arch/s390/kernel/vtime.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -31,11 +31,10 @@ static DEFINE_PER_CPU(struct vtimer_queue, virt_cpu_timer);
* Update process times based on virtual cpu times stored by entry.S
* to the lowcore fields user_timer, system_timer & steal_clock.
*/
void account_process_tick(struct task_struct *tsk, int user_tick)
static void do_account_vtime(struct task_struct *tsk, int hardirq_offset)
{
cputime_t cputime;
__u64 timer, clock;
int rcu_user_flag;
struct thread_info *ti = task_thread_info(tsk);
__u64 timer, clock, user, system, steal;

timer = S390_lowcore.last_update_timer;
clock = S390_lowcore.last_update_clock;
Expand All @@ -44,59 +43,47 @@ void account_process_tick(struct task_struct *tsk, int user_tick)
: "=m" (S390_lowcore.last_update_timer),
"=m" (S390_lowcore.last_update_clock) );
S390_lowcore.system_timer += timer - S390_lowcore.last_update_timer;
S390_lowcore.steal_clock += S390_lowcore.last_update_clock - clock;
S390_lowcore.steal_timer += S390_lowcore.last_update_clock - clock;

cputime = S390_lowcore.user_timer >> 12;
rcu_user_flag = cputime != 0;
S390_lowcore.user_timer -= cputime << 12;
S390_lowcore.steal_clock -= cputime << 12;
account_user_time(tsk, cputime, cputime);
user = S390_lowcore.user_timer - ti->user_timer;
S390_lowcore.steal_timer -= user;
ti->user_timer = S390_lowcore.user_timer;
account_user_time(tsk, user, user);

cputime = S390_lowcore.system_timer >> 12;
S390_lowcore.system_timer -= cputime << 12;
S390_lowcore.steal_clock -= cputime << 12;
system = S390_lowcore.system_timer - ti->system_timer;
S390_lowcore.steal_timer -= system;
ti->system_timer = S390_lowcore.system_timer;
if (idle_task(smp_processor_id()) != current)
account_system_time(tsk, HARDIRQ_OFFSET, cputime, cputime);
account_system_time(tsk, hardirq_offset, system, system);
else
account_idle_time(cputime);
account_idle_time(system);

cputime = S390_lowcore.steal_clock;
if ((__s64) cputime > 0) {
cputime >>= 12;
S390_lowcore.steal_clock -= cputime << 12;
steal = S390_lowcore.steal_timer;
if ((s64) steal > 0) {
S390_lowcore.steal_timer = 0;
if (idle_task(smp_processor_id()) != current)
account_steal_time(cputime);
account_steal_time(steal);
else
account_idle_time(cputime);
account_idle_time(steal);
}
}

/*
* Update process times based on virtual cpu times stored by entry.S
* to the lowcore fields user_timer, system_timer & steal_clock.
*/
void account_vtime(struct task_struct *tsk)
void account_vtime(struct task_struct *prev, struct task_struct *next)
{
cputime_t cputime;
__u64 timer;

timer = S390_lowcore.last_update_timer;
asm volatile (" STPT %0" /* Store current cpu timer value */
: "=m" (S390_lowcore.last_update_timer) );
S390_lowcore.system_timer += timer - S390_lowcore.last_update_timer;

cputime = S390_lowcore.user_timer >> 12;
S390_lowcore.user_timer -= cputime << 12;
S390_lowcore.steal_clock -= cputime << 12;
account_user_time(tsk, cputime, cputime);
struct thread_info *ti;

do_account_vtime(prev, 0);
ti = task_thread_info(prev);
ti->user_timer = S390_lowcore.user_timer;
ti->system_timer = S390_lowcore.system_timer;
ti = task_thread_info(next);
S390_lowcore.user_timer = ti->user_timer;
S390_lowcore.system_timer = ti->system_timer;
}

cputime = S390_lowcore.system_timer >> 12;
S390_lowcore.system_timer -= cputime << 12;
S390_lowcore.steal_clock -= cputime << 12;
if (idle_task(smp_processor_id()) != current)
account_system_time(tsk, 0, cputime, cputime);
else
account_idle_time(cputime);
void account_process_tick(struct task_struct *tsk, int user_tick)
{
do_account_vtime(tsk, HARDIRQ_OFFSET);
}

/*
Expand All @@ -105,21 +92,21 @@ void account_vtime(struct task_struct *tsk)
*/
void account_system_vtime(struct task_struct *tsk)
{
cputime_t cputime;
__u64 timer;
struct thread_info *ti = task_thread_info(tsk);
__u64 timer, system;

timer = S390_lowcore.last_update_timer;
asm volatile (" STPT %0" /* Store current cpu timer value */
: "=m" (S390_lowcore.last_update_timer) );
S390_lowcore.system_timer += timer - S390_lowcore.last_update_timer;

cputime = S390_lowcore.system_timer >> 12;
S390_lowcore.system_timer -= cputime << 12;
S390_lowcore.steal_clock -= cputime << 12;
system = S390_lowcore.system_timer - ti->system_timer;
S390_lowcore.steal_timer -= system;
ti->system_timer = S390_lowcore.system_timer;
if (in_irq() || idle_task(smp_processor_id()) != current)
account_system_time(tsk, 0, cputime, cputime);
account_system_time(tsk, 0, system, system);
else
account_idle_time(cputime);
account_idle_time(system);
}
EXPORT_SYMBOL_GPL(account_system_vtime);

Expand Down Expand Up @@ -490,8 +477,8 @@ void init_cpu_vtimer(void)
/* kick the virtual timer */
S390_lowcore.exit_timer = VTIMER_MAX_SLICE;
S390_lowcore.last_update_timer = VTIMER_MAX_SLICE;
asm volatile ("SPT %0" : : "m" (S390_lowcore.last_update_timer));
asm volatile ("STCK %0" : "=m" (S390_lowcore.last_update_clock));
asm volatile ("SPT %0" : : "m" (S390_lowcore.last_update_timer));

/* enable cpu timer interrupts */
__ctl_set_bit(0,10);
Expand Down

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